ZURICH, SWITZERLAND—Tooth wear and the age of the individual at the time of death can modify the shape of a hominid’s mandible, according to Ann Margvelashvili of the University of Zurich. She and her team examined four 1.77 million-year-old jaws discovered at the site of Dmanisi in the Republic of Georgia, and found that that the high degree of variation among the individuals’ teeth could be attributed to gum disease and the use of toothpicks. “Progressive tooth wear triggers bone remodeling processes that substantially modify the shape of the jaw during an individual’s lifetime. These effects are typically underestimated when attributing fossil hominid jaws to different species,” she explained.